Optical transmission module and manufacturing method of the same

ABSTRACT

[Problems] To accommodate a plurality of optical semiconductor elements in one package with their optical axes aligned highly precisely. 
     [Means for Solving the Problems] An optical transmission module includes an optical transmission unit, a carrier to become a base, a semiconductor optical amplification element mounted on the carrier through a first sub-carrier, first and second lenses fixed on the carrier through first and second lens holders, an element supporting member and an optical isolator fixed on the carrier, a third lens holder supported by the element supporting member, a third lens and a small carrier individually fixed in the third lens holder, and a semiconductor laser element mounted on the small carrier through a second sub-carrier.

TECHNICAL FIELD

The present invention relates to an optical transmission module used foran optical communication system and a manufacturing method thereof, inparticular, to an optical transmission module including a plurality ofoptical devices such as a semiconductor laser, a semiconductor opticalamplifier, and the like in a same package and a manufacturing methodthereof.

BACKGROUND ART

Along with increase in demand for optical communication in recent years,an optical communication system in smaller size with lower cost isstrongly required to be provided. To construct an optical communicationsystem with high reliability and low cost, it is important that thesystem can transmit data for a long distance without relay. As a way toperform it, an optical fiber amplifier and an optical semiconductoramplifier have been known. In the former case, an Er doped optical fiberis excited by an LD module for excitation. However, it needs a very longEr doped optical fiber and a very large LD module for excitation, sothat it is disadvantageous in that it becomes expensive, and a systemtends to be large. On the other hand, the latter, i.e. the opticalsemiconductor amplifier, has the same structure as a semiconductor laserelement, so that the latter is advantageous to a system to be downsized,in addition, the latter enables a system to be constructed in lower costcomparing to the former case.

FIG. 21 is a configuration diagram showing a related opticaltransmission module using an optical semiconductor amplifier. In thepresent specification, a direction of an optical axis is called as a Zdirection, a direction vertical to a main surface of a carrier to be abase is called as a Y direction, and a direction orthogonal to the Y andthe Z directions is called as an X direction.

As shown in FIG. 21, an optical transmission module 290 includes a lasermodule 280 incorporating an optical modulator and an optical amplifiermodule 260.

The laser module 280 is composed of a laser element 281, a lens 282, alens holder in a U-shape (unillustrated, see FIG. 22), an opticalisolator 283, an element carrier 284, a peltier device 285, a lens 286,a ferrule 287, an optical fiber 288, a package 289, and so on.

The laser element 281 incorporates an optical modulator, and outputs amodulated optical signal (on optical signal). The lens 282 is in astructure with a transmissive glass part set in an alloy frame, and itcollects optical signals outputted from the laser element 281 in a sideof the optical isolator 283. The optical isolator 283 prevents the lightfrom returning to the laser element 281. On the device carrier 284, thelaser element 281, the lens 282, and the optical isolator 283 are fixedin alignment with a same optical axis. The peltier device 285 maintainsa constant temperature of the laser element 281 so that the opticalfiber 288 outputs the modulated optical signal stably. The lens 286collects the optical signal transmitted through the optical isolator 283on the optical fiber 288. The ferrule 287 fixes the optical fiber 288 onthe package 289 through the lens 286. The optical fiber 288 guides theoptical signal outputted from the laser element 281 to outside thepackage 289.

The optical amplifier module 260 is composed of an optical fiber 261, aferrule 262, a lens 263, a lens 264, a semiconductor optical amplifyingelement 265, a lens 266, a lens 267, a ferrule 268, an optical fiber269, a carrier 270, a peltier device 271, a package 272, and so on. Inother words, the optical amplifier module 260 is composed of thesemiconductor optical amplifying element 265 which amplifies and outputsan incident light, the optical fibers 261 and 269 for input and output,and the lenses 263, 264, 266, 267 which couple the semiconductor opticalamplifying element 265 with input/output optical fibers 261, 269 withhigh efficiency.

The optical fiber 261 includes a splicing part (a fusion splicing part)273 formed an edge thereof for splicing itself and the optical fiber288, and guides the optical signal outputted from the laser module 280to the optical amplifier module 260. The ferrule 262 fixes the opticalfiber 261 on the package 272 through the lens 263. The lens 264 collectsthe optical signal transmitted through the lens 263 on the semiconductoroptical amplifying element 265. The semiconductor optical amplifyingelement 265 operates on the same principle as the semiconductor laser,and produces an optical amplification effect for light injected fromoutside by using a gain function in a semiconductor active regiondepending on current injection. The lens 266 collects the optical signalamplified by the semiconductor optical amplifying element 265 on thelens 267. To align optical axes of the lens 264 and the semiconductoroptical amplifying element 265, as well as optical axes of thesemiconductor optical amplifying element 265 and the lens 266, thelenses 264 and 266 are fixed on the carrier 270 through U-shaped lensholders (unillustrated, refer to FIG. 22). The ferrule 268 fixes theoptical fiber 269 on the package 272 through the lens 267. The opticalfiber 269 guides the optical signal amplified by the semiconductoroptical amplifying element 265 to outside the package 272.

To achieve a long-distance transmission without relay, the opticalsignal outputted from the laser element 281 is not sufficient.Therefore, in the optical transmission module 290, the optical signalfrom the laser element 281 is amplified by current injection at thesemiconductor optical amplifying element 265 so as to be high-poweroutput light, and is outputted from the optical fiber 269. The lasermodule 280 and the optical amplifier module 260 are produced separately,and then the optical fiber 288 of the laser module 280 and an input sideof the optical fiber 261 of the optical amplifier module 260 areconnected by fusion splicing to be used.

In the optical transmission module shown in FIG. 21, the lenses 264,266, 282 and the like are fixed on the carriers by laser welding (YAGlaser welding) using the U-shaped lens holder so that the optical axesthereof are aligned to the optical axis of the semiconductor opticalamplifying element 265 and the laser element 281, and that a focal pointis placed on a prescribed position. FIG. 22 is an exploded perspectiveview describing a method for fixing the lens 282 using the lens holder.The lenses 264 and 266 are also welded and fixed in the same way, sothat the fixing method only for the lens 282 will be presentedhereinafter.

A lens holder 291 includes a plate-like base part 291 a and a pair ofholding plates 291 b and 291 c provided vertically to the platy basepart 291 a. An interval between the holding plates 291 b and 291 c isdesigned to be almost equivalent to a width of the lens 282.Accordingly, the lens 282 can be held in between the holding plates 291b and 291 c. The lens 282 is adjusted and fixed as follows. The lensholder 291 in which the lens 282 is set is placed on the carrier 284 onwhich the laser element 281 is bonded by die bonding. Then, whilecausing the laser element 281 to emit light, the lens and the lensholder are moved in the three axes directions for adjusting the lens 282in an optimal position.

After the adjustment, the lens holder 291 and the carrier 284 are weldedby laser welding at plural points (at 4 points, for example), so thatthe lens holder 291 is fixed. Accordingly, the position of the lens 282in the X direction is fixed. Next, the lens 282 is moved again, upwardand downward (in the Y direction), and backward and forward (in the Zdirection) with respect to the lens holder 291, for adjusting the lens282 in an optical position in the Y direction and the Z direction, andthen the lens 282 and the lens holder 291 are welded by laser welding atplural points (at 4 points, for example). As described, because the lensholder 291 and the lens 282 are combined together, the lens 282 can beadjusted and fixed optimally in a position to which the laser element281 emits light with respect to the three axes of X, Y, Z.

However, this related optical transmission module (hereinafter, referredto as a separated optical transmission module) is composed of a lasermodule and an optical amplifier module in separate packages, so thateach of the packages, the input/output optical fibers, and the splicepart of the optical fibers require a certain area and volume to behoused respectively. Therefore, the module is limited in downsizing andit is disadvantageous in that the module becomes large in size.

So, housing the laser element and the semiconductor optical amplifyingelement in a same package is proposed (refer to in Patent Documents 1and 2, for example). In an optical transmission module proposed by thosePatent Documents (hereinafter, an integrated optical transmissionmodule), a laser element and a semiconductor optical amplifying elementare bonded on a carrier by die bonding, and a plurality of lenses isfixed on the carrier using U-shaped lens holders respectively.Alternatively, a laser element is bonded on a carrier by die bonding,and a small carrier on which a semiconductor optical amplifying elementis bonded by die bonding is fixed on the carrier using a U-shapedholder, and also a plurality of lenses is fixed on the carrier usingU-shaped lens holders respectively.

Patent Document 1: Japanese Patent Application Laid-open No. 2005-17839Patent Document 2: Japanese Patent Application Laid-open No. 2005-19820DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

As described above, in the related optical transmission modules, both inthe separated type and the integrated type, a U-shaped holder (such as alens holder and an optical amplifier element holder) is used to adjustpositions of a lens and a semiconductor optical amplifying element andso on, so that optical axes of each device are aligned.

Meanwhile, metal melts and coagulates during processes of laser beamirradiation and cooling in welding, which causes heat extension andcontraction in the holder, and a thermal stress is generated therein,too. Along with those processes, the holder is placed out of a rightposition and a right angle. When the holder and the small carrier onwhich the lens and the semiconductor optical amplifying element arebonded by die bonding are welded, the same problem also occurs. The lensand the semiconductor optical amplifying element are fixed out of rightpositions and right angles, which ends up a misalignment state withrespect to the optical axis.

In a case of the related separated type shown in FIG. 21, even if thelenses 264 and 266 in the optical amplifier module are misaligned andfixed with respect to the optical axis, the effect of the misalignmentcan be decreased or eliminated by adjusting the positions of the lenses263 and 267 to be fixed. Further, in this related case, somemisalignment is not to be serious defect if any, because there are widemargins for the alignment.

However, in the case of the integrated optical transmission module,emitting light from the laser element needs to be injected into anactive layer of the semiconductor optical amplifying element, and thatrequires high accuracy for the alignment between the laser device andthe semiconductor optical amplifying device. In addition, the effect ofmisalignment cannot be compensated or eliminated, which is unlike thecase of the separated optical transmission module where the compensationor elimination is performed by the lenses fixed later. In other words,the separated optical transmission module can be saved as anon-defective product because optical coupling rate does not decrease somuch even if lenses of the module are fixed in a misalignment state oran angular misalignment state to some extent. On the other hand, theintegrated optical transmission module tends to be a defective productwith a high possibility when it includes even a slight misalignment or aslight angular misalignment which causes extreme drop in the opticalcoupling rate. Therefore, the integrated optical transmission modulerequires extremely high accuracy for its assembling. Thus, an efficientworkability is not achieved, and a high yield cannot be expected.

An object of the present invention is to solve the aforementionedproblem with the related technique, and to provide an integrated opticaltransmission module produced with efficient workability and highaccuracy.

Means of Solving the Problems

To achieve the aforementioned object, an optical transmission moduleaccording to the present invention includes: a first optical devicedisposed at an output side; a second optical device which is disposedwith its optical axis being aligned with an optical axis of the firstoptical device; a carrier on which either the first or the secondoptical device is fixed; an element support member having a firstsurface parallel to the optical axes and a second surface vertical tothe optical axes; a package for housing the first and the second opticaldevices, the carrier and the element support member; and a light guidingunit for guiding light emitted from the first optical device towardoutside the package; wherein the element support member is fixed on thecarrier at the first surface of the member, and the other one of thefirst and the second optical devices is fixed on the second surface ofthe element support member.

A manufacturing method of an optical transmission module according tothe present invention, the optical transmission module includes a firstoptical device disposed in an output side, a second optical device whichis disposed with its optical axis being aligned with an optical axis ofthe first optical device, a carrier on which either the first or thesecond optical device is fixed, an element support member having a firstsurface parallel to the optical axes and a second surface vertical tothe optical axes, a package for housing the first and the second opticaldevices, the carrier, and the element support member, and a lightguiding unit for guiding light emitted from the first optical devicetoward outside the package, wherein the element support member is fixedon the carrier at the first surface of the member, and the other one ofthe first and the second optical devices is fixed on the second surfaceof the element support member, the method includes the steps of:

(1) fixing either the first or the second optical device on the carrier;(2) adjusting a position of the element support member while the otherone of the first and the second optical devices closely contacts withthe second surface of the device support member, and fixing the elementsupport member on the carrier;(3) aligning an optical axes of the first optical device and the secondoptical device while the other one of the first and the second opticaldevices is pressed on the second surface of the element support member,and fixing the other one of the first and the second optical devices onthe second surface of the element support member.

ADVANTAGEOUS EFFECT OF THE INVENTION

According to the present invention, either the first or the secondoptical device is fixed on the carrier, and the other is closelycontacted with the second surface (a surface vertical to the opticalaxis) of the element support member and fixed thereon. According to thisstructure, after the optical axis of the other optical device is alignedwith the optical axis of the remaining optical device in an X-Y plainsurface, the other optical device can be fixed on the surface. That canminimize a misalignment in the X and Y directions generated due tothermal extension and contraction of metal in welding of the otheroptical device, and can keep an angular misalignment in a low level.Further, workability in assembly processes is improved. Thus, accordingto the present invention, an optical transmission module in small-size,with high quality and stable characteristic can be manufactured with ahigh yield.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, exemplary embodiments of the invention will be described in detailwith reference to drawings.

First Exemplary Embodiment

FIG. 1 is a cross-sectional view showing an optical transmission moduleaccording to a first exemplary embodiment of the invention. FIG. 2 is aperspective view showing an optical transmission unit in the firstexemplary embodiment.

As shown in FIGS. 1 and 2, an optical transmission module 1 is composedof a package 111, a peltier device 112 which is placed in the package111 and controls temperature of an optical transmission unit 2, theoptical transmission unit 2 placed on the peltier device 112, a fibersupport 113 which is put on an opening of the package 111, a ferrule 114supported by the fiber support 113, and an optical fiber 115 held by theferrule 114.

The optical transmission unit 2 is composed of a carrier 116 whichbecomes a base, a first optical device 118 which is attached on thecarrier 116 through a first sub carrier 117, a first and a second lens120, 122 fixed on a carrier through a first and a second lens holder119, 121, an element support member 123 and the optical isolator 124both of which are fixed on the carrier, a third lens holder 125supported by the element support member 123, a third lens 126 and asmall carrier 127 fixed on the third lens holder 125 respectively, and asecond optical device 129 attached on the small carrier 127 through asecond sub carrier 128.

In the optical transmission module 1 shown in FIGS. 1 and 2, an opticalsignal emitted from the second optical device 129 is collected in theoptical isolator 124 side through the third lens 126, and the opticalsignal passed through the optical isolator 124 is collected on the firstoptical device 118 through the second lens 122. The optical signal isamplified and emitted by the first optical device, and is injected intothe optical fiber 115 through the first lens 120. The optical isolator124 prevents the optical signal from returning to the second opticaldevice 129. The peltier device 112 maintains the second optical device129 and the first optical device 118 at a constant temperature.

The element support member 123 is in a square cylindrical shape having asquare shaped cross-section, and openings 123 a for transmitting lightare provided on two surfaces thereof facing the optical axis direction.The element support member 123 is fixed on the carrier 116 by welding atwelding points 47 a and 48 a while a bottom surface of the memberclosely contacts with the carrier 116. Further, as shown in FIG. 2, thethird lens holder 125 includes a lens holding part 125 a in a U-shapefor holding the third lens and a plate-like upright part 125 b which isvertically upright and has a light transmissive hole (125 a in FIG. 1).The third lens holder 125 is fixed on the element support member 123 bywelding at welding points 45 a and 46 a while a surface in the elementsupport member 123 side of the upright part 125 b closely contacts witha side surface of the element support member 123.

The second optical device 129 is bonded on the second sub carrier 128 bydie bonding using AuSn solder or the like, and the second sub carrier128 is soldered to the small carrier 127 using the AuSn solder or thelike. The third lens 126 is fixed on the third lens holder 125 bywelding at welding points 41 a and 42 a, and the third lens holder 125is fixed on the small carrier 127 by welding at welding points 43 a and44 a. Accordingly, the second optical device unit 3 composed of thethird lens holder 125, the third lens 126, the small carrier 127, thesecond sub carrier 128 and the second optical device 129 is fixed on theelement support member 123 as a whole.

The optical isolator 124 is fixed on the carrier 116 by welding atwelding points 49 a and 50 a. The second lens 122 is fixed on the secondlens holder 121 by welding at welding points 51 a and 52 a. The secondlens holder 121 is fixed on the carrier 116 by welding at welding points53 a and 54 a. The first optical device 118 is bonded on the first subcarrier 117 by die bonding using the AuSn solder or the like, and thefirst sub carrier 117 is soldered to the carrier 116 with the AuSnsolder or the like. The first lens 120 is fixed on the first lens holder119 by welding at welding points 55 a and 56 a, and the first lensholder 119 is fixed on the carrier 116 by welding at welding points 57 aand 58 a.

At the welding points 41 a-58 a, laser welding is performed using YAGlaser, for example. In FIGS. 1 and 2, welding points 41 b-58 b(unillustrated) are provided in an invisible opposite side from thewelding points 41 a-58 a symmetrically. It is desirable that, as anirradiation condition for a laser beam in welding, a laser output power,a laser irradiation time, and laser output distribution for obtaining asufficient welding strength and minimizing a misalignment in welding beexamined experimentally and optimized in advance. Further details forthe above will be provided. Considering minimizing a thermal contractionpower generated at a coagulation and cooling stage in metal welding,that is, minimizing a misalignment due to welding, a laser output isdesirably as low as possible with which the welding can be performed,and a laser irradiation time is desirably as short as possible withwhich the welding can be performed. In order to decrease the laseroutput and to shorten the laser irradiation time while welding isperformable, it is effective to thin the thickness of the weldingpoints. Further, it is desirable that laser output distribution belowered gradually to prevent the welding points from having fissuressuch as cracks, or having a residual stress. The fissures and cracks atthe welding points heavily affect the welding strength, and the residualstress heavily affects reliability. Since those laser irradiationconditions are affected a lot by a shape and a condition of weldingpoint, it is desirable that the laser irradiation condition beexperimentally examined and optimized at each welding point with variousshapes and with the misalignments and welding stresses.

Second Exemplary Embodiment

FIG. 3 is a perspective view showing an optical transmission unitaccording to second exemplary Embodiment of the invention. The opticaltransmission unit 2 is mounted within a package to which a peltierdevice, a ferrule and the like are attached, as well as the case in thefirst exemplary embodiment shown in FIG. 1.

In FIG. 3, the same components as in FIG. 2 have identical referencenumerals, and the same explanation will be omitted accordingly. In theexemplary embodiment, the third lens holder 125 is in a simple U-shape.The small carrier 127 is formed such that a longitudinal section of thesmall carrier 127, which is parallel to the optical axis, is anL-shaped. The small carrier 127 closely contacts with the elementsupport member 123, and welded to the element support member 123 atwelding point 59 a and 60 a. That is, in the exemplary embodiment, thesmall carrier 127 includes an element mounting part 127 a which isparallel to the carrier 116 and an upright part 127 b which risesvertically from the element mounting part 127 a and is provided with alight transmissive hole. The small carrier 127 closely contacts with aside of the element support member 123 at a surface in the opticalisolator 124 side of the upright part 127 b, and is fixed with theelement support member 123. To the element mounting part 127 a of thesmall carrier 127, the second sub carrier 128 to which the secondoptical device 129 is bonded by die bonding is soldered, and inaddition, the third lens holder 125 on which the third lens 126 iswelded and fixed, is welded and fixed. Those of the third lens holder125, the third lens 126, the small carrier 127, the second sub carrier128 and the second optical device 129 composes a second optical deviceunit 3 which is mounted on the element support member 123.

In the second exemplary embodiment shown in FIG. 3, the opticaltransmission unit becomes slightly larger (within a few millimeters) inthe Z direction than that of the first exemplary embodiment. The reasonscan be explained with reference to FIG. 4.

Before the optical transmission unit 2 shown in FIGS. 2 and 3 isassembled, the second optical device unit 3 is assembled. At that time,the third lens 126 is aligned with the second optical device 129(focusing). The alignment is performed, as shown in FIG. 4( a), whilethe third lens 126 is closely contacted with a vertical part of thethird lens holder 125.

In the case of the second exemplary embodiment, a margin for adjustmentis needed in between the third lens 126 and the small carrier 127 forthe alignment, so that there is a gap, which is indicated with “a”, inbetween the third lens 126 and the small carrier 127, as shown in FIG.4( b). Therefore, due to the gap “a”, the optical transmission unit ofthe second exemplary embodiment is slightly larger in size (within a fewmillimeters) than the optical transmission unit of the first exemplaryembodiment in the Z direction.

Third Exemplary Embodiment

FIG. 5 is a perspective view of an optical transmission unit accordingto a third exemplary embodiment of the invention, and FIGS. 6( a) and6(b) are cross-sectional views respectively taken along lines A-A andB-B in FIG. 5.

The optical transmission unit 2 of the third exemplary embodiment ismounted within a package to which a peltier device, a ferrule and thelike are attached as well as the case in the first exemplary embodiment.In FIG. 5, the same components as in FIG. 2 have identical referencenumerals, and the same explanation will be omitted accordingly.

In the exemplary embodiment, the element support member 123 includes asmall carrier holding part 123 a having a cross-section, which isvertical to the optical axis, of U-shaped, for housing the small carrier127, and an upstanding part 123 b having a surface vertical to theoptical axis. The element support member 123 closely contacts with anupper surface of the carrier 116 at a bottom surface of the member, andis welded with the carrier 116 at the welding points 47 a and 48 a. Thesmall carrier 127 is held in the small carrier holding part 123 a of theelement support member 123. The small carrier 127 is fixed with theelement support member 123 while a side surface of the small carrierclosely contacts with a surface of the upstanding part 123 b of theelement support member 123. The element support member 123 and the smallcarrier 127 are welded together at welding points 61 a and 62 a.Further, the upstanding part 123 b of the element support member 123 isprovided with openings 63 a-67 a for welding, and the welding with thesmall carrier 127 is performed at bottom parts of the openings 63 a-67a.

The opening 65 a for welding is a counter-bored hole in an example shownin FIG. 6( b), however, the opening 65 a may be a stepped hole as shownin FIG. 6C. The upstanding part 123 b of the element support member 123is provided in an opposite side to a light emitting direction from thesecond optical device 129 in the exemplary embodiment, however, theupstanding part 123 b may be provided inversely in a side of the lightemitted direction of the second optical device 129 (namely, in anoptical isolator 124 side). In the second exemplary embodiment, acollected point of outgoing light from the third lens 126 iscomparatively away from the welding point where the small carrier 127and the element support member 123 are welded. Accordingly, a strictangular alignment is required in welding. If the element support member123 rotates 180 degrees to make the upstanding part 123 b be in theoptical isolator 124 side, the accuracy requirement can be eased.Further, according to a modified example shown in FIG. 8( b), which willbe described later, the accuracy requirement can be eased in the samemanner.

An essential point in the element support member 123 used in the presentinvention is that the element support member includes a surface (a firstsurface) fixed on the carrier closely, and a surface (a second surface)vertical to the optical axis and fixing the small carrier and the lensholder closely thereon. Thus, a shape of the element support member isnot limited specifically.

FIGS. 7( a) and 7(b) are perspective views showing modified examples ofthe element support member 123 used in the first exemplary embodiment.In the example shown in FIG. 7( a), the element support member 123 is ina plate-like shape. Meanwhile, in the example shown in FIG. 7( b), theelement support member 123 has a U-shaped cross-section. The elementsupport member 123 shown in FIGS. 7( a) and 7(b) can be used also in theoptical transmission module of the second exemplary embodiment.

FIGS. 8( a) and 8(b) are perspective views showing modified examples ofthe third exemplary embodiment. FIG. 8( a) is the perspective view ofthe second optical device unit 3 from the optical isolator side. In FIG.8( a), the element support member 123 includes an upright part 123 c atan edge of the small carrier holding part 123 a. The small carrier 127also includes an upright part 127 b at an edge of an element mountingpart 127 a. Further, the upright part 127 b of the small carrier 127closely contacts with the upright part 123 c of the element supportmember 123, and the small carrier 127 is fixed on the element supportmember 123 by welding at welding points 68 b and 69 b, in addition tothe welding points 61 b and 62 b. In the example shown in FIG. 8( b),the upright parts 123 c and 127 b of the element support member 123 andthe small carrier 127 are provided in the optical isolator 124 side.Further, the small carrier holding part 123 a has a U-shapedcross-section in the third exemplary embodiment and FIG. 8, however, thesmall carrier holding part may have a simple plate-like shapedcross-section so that its cross-sections vertical to the optical axisare entirely in a square shape.

In aforementioned exemplary embodiments 1-3, the second optical devicesection side is fixed to the element support member. However, the firstoptical device section side may be fixed inversely. In that case, thefirst optical device is mounted on the small carrier through the firstsub carrier, and the second optical device is on the carrier through thesecond sub carrier. Further, as in the case of the first exemplaryembodiment, the second lens holder is welded and fixed on the elementsupport member, or, alternatively, as in the cases of the second and thethird exemplary embodiments, the small carrier is welded and fixed onthe element support member.

When the lenses, the lens holders, or the element support member isfixed with a welding measure such as the YAG laser welding in theoptical transmission module according to the present invention, it isdesirable that the carrier 16, the lens holders, frame parts of thelenses, and the element support member 23 be made of metal such askovar, iron-nickel-cobalt alloy, which has a low thermal expansioncoefficient and is suitable for laser welding. When those components areprocessed on their surface, it is desirable that at least welding pointsin their surface be prevented from gold plating, or have extremely thingold plating if they need to be plated. The reason is that gold platingcauses a crack and a fissure at the welding points, and welding qualitybecomes deteriorated. Consequently, it causes a problem for degradationof reliability. Specifically, considering that the semiconductor deviceis bonded on the sub carrier by die bonding using solder such as AuSnand the sub carrier is bonded on the carrier 16 by die bonding usingsolder such as AuSn, it is desirable that the surface of the carrier 16be plated with gold for performing soldering with high reliability.However, the element support member 23 is generally plated with brushednickel, and if one component of the components welded is gilded, thereis large difference in the coefficients of the thermal extension betweenthe gold plated component and components plated with other material thangold because the gold has a very high coefficient of thermal expansion.That increases the thermal contraction stress generated in welding.Thus, when a component is gilded, the plating is gilded as thinly aspossible.

In a manufacturing method of an optical transmission module according tothe present invention, the YAG laser welding is effectively used forfixing the element support member on the carrier, or fixing the smallcarrier and the lens holder on the element support member. However,welding methods other than the YAG laser welding may be used. Further,brazing, soldering, and adhesion can be used for fixing, in stead ofwelding. In a case with adhesion, the carrier, the lens holders, thelens frames, the element support member 23, the sub carrier and thesmall carrier can be made of any materials. However, those are desirablymade of metal materials with a low thermal expansion coefficient,considering long-term reliability. In addition, it is desirable to useadhesive having the thermal expansion coefficient that is as close aspossible to the thermal expansion coefficient of an adherend component.

In aforementioned first to third exemplary embodiments, as a specificexample, the first optical device is assumed to be an optical amplifierdevice, and the second optical device is assumed to be a laser device.However, the present invention is not limited by the above example. Forinstance, a passive optical circuit device may be used as the secondoptical device. In that case, light emitted from the first opticaldevice as an optical amplifier device is received by the second opticaldevice, and it is returned to the first optical device after performinga signal processing at the second optical device. The first opticaldevice amplifies the light returned from the second optical device, thenoutputs the optical signal to outside through an optical fiber.Furthermore, in aforementioned first to third exemplary embodiments, twooptical devices, i.e. the first and the second optical devices, aremounted within the package. However, the number of optical devicesmounted therein is not limited to be two, and three or more opticaldevices may be mounted. For example, the optical devices may be the onein which an optical signal emitted from a semiconductor laser device isamplified by multistage semiconductor optical amplifying elements, orthe one in which an optical circuit device composing a passive opticalprocessing circuit may be arranged in between a semiconductor laserdevice and a semiconductor optical amplifying device, or arranged behindan optical amplifying device. When a third optical device is provided inaddition to the first and the second optical devices, the third opticaldevice is fixed on the element support member through a small carrier ora lens holder to be placed next to the third optical device.

First Example

FIG. 9 is a cross-sectional view showing a first example of the presentinvention. FIG. 10 is a perspective view showing an optical transmissionunit according to the first example. As shown in FIGS. 9 and 10, anoptical transmission module 1 is composed of a package 11, a peltierdevice 12 placed in the package 11 to control temperature of an opticaltransmission unit 2, the optical transmission unit 2 placed on thepeltier device 12, a fiber support 13 attached to an opening part of thepackage 11, a ferrule 14 supported by the fiber support 13, and anoptical fiber 15 held by the ferrule 14.

The optical transmission unit 2 is composed of a carrier 16 which is tobe a base, a semiconductor optical amplifying element 18 attached on thecarrier 16 through a first sub carrier 17, a first and a second lenses20 and 22 fixed on the carrier 16 through a first and a second lensholders 19 and 21, a element support member 23 and an optical isolator24 which are fixed on the carrier 16, a third lens holder 25 supportedby the element support member 23, a third lens 26 and a small carrier 27which are fixed on the third lens holder 25, and a semiconductor laserdevice 29 attached on the small carrier 27 through a second sub carrier28.

In the optical transmission module shown in FIGS. 1 and 2, an opticalsignal emitted from the semiconductor laser device 29 is collected on aside of the optical isolator 24 through the third lens 26. The opticalsignal passed through the optical isolator 24 is collected on thesemiconductor optical amplifying element 18 through the second lens 22.The optical signal is amplified by the semiconductor optical amplifyingelement 18 and emitted, and is injected into the optical fiber 15through the first lens 20. The optical isolator 24 prevents the opticalsignal from returning to the semiconductor laser device 29. The peltierdevice 12 maintains the semiconductor laser device 29 and thesemiconductor optical amplifying element 18 at a constant temperature.

The element support member 23 is a square cylinder having a squareshaped cross-section, and its two surfaces facing the optical axisdirection are provided with openings 23 a to transmit light. The elementsupport member 23 is fixed on the carrier 16 by welding at weldingpoints the 47 a and 48 a while a bottom surface of the element supportmember closely contacts with the carrier 16. The third lens holder 25includes a lens holding part 25 a in a U-shape for holding the thirdlens 26 and a plate-like upright part 25 b rising vertically andprovided with a light transmissive hole. The third lens holder 25 isfixed on the element support member 23 by welding at welding points the45 a and 46 a while the side of the upright part 25 b on the surface ofan element support member 23 closely contacts with the side surface ofthe element support member 23.

The semiconductor laser device 29 is bonded with the second sub carrier28 by die bonding using the AuSn solder or the like, and the second subcarrier 28 is soldered to the small carrier 27 using the AuSn solder orthe like. The third lens 26 is fixed on the third lens holder 25 bywelding at the welding points 41 a and 42 a. The third lens holder 25 isfixed on the small carrier 27 by welding at the welding points 43 a and44 a. Accordingly, the second optical device unit 3 which is composed ofthe third lens holder 25, the third lens 26, the small carrier 27, thesecond sub carrier 28 and the semiconductor laser device 29 is fixed onthe element support member 23 as a whole. The optical isolator 24 isfixed on the carrier 16 by welding at the welding points 49 a and 50 a.The second lens 22 is fixed on the second lens holder 21 by welding atthe welding points 51 a and 52 a, and the second lens holder 21 is fixedon the carrier 16 by welding at the welding points 53 a and 54 a. Thesemiconductor optical amplifying element 18 is bonded to the first subcarrier 17 by die bonding using the AuSn solder or the like, and thefirst sub carrier 17 is soldered to the carrier 16 with the AuSn solderor the like. The first lens 20 is fixed on the first lens holder 19 bywelding at the welding points 55 a and 56 a. The first lens holder 19 isfixed on the carrier 16 by welding at the welding points 57 a and 58 a.Laser welding is performed at the welding points 41 a-58 a, using theYAG laser for example. In FIGS. 1 and 2, welding points 41 b-58 b(unillustrated) are provided in an invisible opposite side from thewelding points 41 a-58 a.

The welding points between the element support member 23 and the thirdlens holder 25 require the highest accuracy in each welding point. Forconvenience of illustration, the drawing shows as if those two arewelded together at two points in one side. However, they are actuallywelded together at three points in one side, six points in total. Tominimize a thermal stress which is generated at a metal solidificationand cooling stage in welding, the thickness of the welding points aredesirably to be thin. So, as shown in FIGS. 11( a) and 11(b), thewending points of the third lens holder 25 are provided with an openingwith a taper part 25 c. Accordingly, the welding can be performed evenif injected laser outputs are decreased, and a misalignment and anangular misalignment along with the welding can be kept in low degree.The reason for having the opening with a thin part inside the third lensholder 25 is to prevent the size in the X direction from increasing. Theshape of the opening at the welding points is not limited by the oneshown in FIG. 11( b). It may be the one which has a thin part 25 asshown in FIG. 11( c). To determine the shape of the opening, it isdesirable to perform an experiment and obtain a shape with which amisalignment can be suppressed at minimum.

Assembly Method for First Example

Next, an assembly (manufacturing) method for optical transmission moduleaccording to the first example will be explained. Firstly, the secondoptical device unit 3 including the semiconductor laser device 29 isassembled. The second sub carrier 28 to which the semiconductor laserdevice 29 is bonded by die bonding is soldered to the small carrier 27using the AuSn solder or the like.

Next, the third lens 26 is aligned on the small carrier 27. That is,while causing the semiconductor laser device 29 to emit light, theoptical fiber is placed at a position where the light from the thirdlens 26 is collected. The optical fiber 24 is connected to an opticalpower meter, and the position of the third lens 26 is adjusted so thatthe optical output is maximized. Then, the third lens holder 25 isinserted in between the small carrier 27 and the third lens 26. Next,the small carrier 27 and the third lens holder 25 are fixed togetherwith the YAG laser welding, and the third lens holder 25 and the thirdlens 26 are fixed together with the YAG laser welding. For this type ofwelding, it is preferable that welding points [the welding points 41 aand 41 b (unillustrated), for example] which are provided to besymmetrical to each other about a vertical line passing through theoptical axis are welded at the same time. After the above processes, thesecond optical device unit 3 including the semiconductor laser device 29is complete.

Next, optical components on the carrier 16 such as lenses and the likeare assembled. Firstly, the semiconductor optical amplifying element 18is bonded on the first sub carrier 17 by die bonding using the AuSnsolder or the like, and the first sub carrier 17 is fixed on the carrier16 with the AuSn solder or the like. As well as the assembly of thethird lens 26, the semiconductor optical amplifying element 18 emitslight, and an optical fiber is placed at a position where the light fromthe first lens 20 is to be collected, then the optical fiber 24 isconnected to an optical power meter. The position of the first lens 20is adjusted with respect to an optical axis of the light emitted fromthe semiconductor optical amplifying element 18 so that the opticaloutput is maximized. After the adjustment, the first lens holder 19 isfixed on the carrier 16 with the YAG laser welding, and the first lens20 is fixed on the first lens holder 19 with the YAG laser welding.

As for the second lens holder 21, the second lens 22, and the carrier16, again in the same manner, causing the semiconductor opticalamplifying element 18 to emit light and an optical fiber is placed at aposition where the light passing through the second lens 21 is to becollected. The optical fiber is connected to the optical power meter,and then, the second lens holder 21 is fixed on the carrier 16, and thesecond lens 22 is fixed on the second lens holder 21 respectively by theYAG laser welding so that the optical output is maximized.

Next, the optical isolator 24 and the second lens 22 are aligned so thatthe centers thereof are substantially corresponding and the light passesthrough the optical isolator 24. Then, the optical isolator 24 and thecarrier 16 are fixed together by the YAG welding.

Next, by referring to FIGS. 12( a)-12(d), a fixing method for theelement support member 23 and the second optical device unit 3 withrespect to the carrier 16 will be explained.

As shown in FIG. 12( a), the element support member 23 and the thirdlens holder are clipped together with a clip 31 to be contacted witheach other on their facing surfaces, and the second optical device unit3 is gripped by a gripper 32. Then, the alignment is performed by movingthem in the X, Y, and Z directions. That is, while causing thesemiconductor laser device 29 and the semiconductor optical amplifyingelement 18 to emit light, and, with measuring the optical output by theoptical power meter 33, the alignment for an optimal position isperformed so that the optical output from the semiconductor opticalamplifying element 18 is maximized.

After the alignment, as shown in FIG. 12( b), a pressure tool 34 pressesthe element support member 23 so that the element support member 23 andthe carrier 16 closely contact with each other. The element supportmember 23 is fixed by the YAG laser welding while in the above state, atthe welding points 47 a and 47 b, 48 a and 48 b. This welding isperformed at least at each two-point provided to be symmetrical to eachother about a surface passing through the optical axis and vertical to amain surface of the carrier 16, i.e. at least at four points in total,at the same time and with the same power. Accordingly, the thermalcontraction power generated at the metal solidification and coolingstage in the welding can be balanced, and a misalignment and an angularalignment in the welding can be kept at the minimum. According to thiswelding, the position of the semiconductor laser device 29 in the Z axisdirection (the optical axis direction) is fixed.

As shown in FIG. 12( c), the second optical device unit 3 is moved againin the movable X, Y directions to be adjusted its position optimally. Inthe adjustment, a pusher 35 pushes the third lens holder 25 and a stressfor the push is increased gradually. The pusher 35 pushes the third lensholder 25 at three push areas 35 a, as shown in FIG. 13( a). At thattime, a barycenter of the push is made to be aligned with the opticalaxis as much as possible (ideally, the barycenter corresponds to theoptical axis). The third lens holder 25 is pushed with its stressgradually increased while the stress to push each of the three areas isbalanced and controlled so that a misalignment with the optical axisdoes not occur. The second optical device unit 3 is released from thegripper 32 while the pusher 35 pushes the third lens holder 25, and thewelding is performed [FIG. 12( d)].

The aforementioned welding is performed firstly at the welding points 45a and 45 b, shown in FIG. 13( b), which are provided to be symmetricalto each other about the optical axis which is in between the weldingpoints 45 a and 45 b. Two of those points are welded at the same timeand with the same power, so that the thermal contraction generated atthe metal solidification and cooling stage in the welding is balanced,and thereby a misalignment of the optical axis of the third lend holder25 can be suppressed at minimum. Next, the welding points 46-1 a and46-1 b, 46-2 a and 46-2 b, which are line-symmetric to each other withrespect to a vertical line passing through the optical axis, are weldedrespectively at the same time and with the same power. When distances ofthose welding points from a vertical line and a horizontal line passingthrough the optical axis are expressed by a, b, c, d, as illustrated,the relationships are defined as a=b, c=d. Further, with respect to thesecond and later welding, the welding may be performed at the weldingpoints 46-1 a and 46-2 b at the same time, also 46-2 a and 46-1 b at thesame time, in which the welding points in each pair are provided to besymmetric to each other about the optical axis, instead of welding thewelding points 46-1 a and 46-1 b, 46-2 a and 46-2 at the same time, inwhich the welding points are provided to be line-symmetric with respectto the vertical line passing through the optical axis. Note that thosewelding points are formed in the taper parts of the openings shown inFIGS. 11( a) and 11(b). The welding points 45 a and 45 b, 46-1 a and46-1 b, 46-2 a and 46-2 b may be arranged in a same distance from theoptical axis. That is, they may be arranged symmetrically on a samecircle centering the optical axis.

After the components to be fixed on the carrier 16 are totally fixed,the carrier 16 is fixed on the peltier device 12 in the package 11 asshown in FIG. 9. Then, while the optical fiber 15 is connected to theoptical power meter (unillustrated) with checking the optical output,the position is adjusted so that the optical output becomes the maximum.Firstly, the fiber support 13 is moved in the X and Y directions foradjustment, and the fiber support 13 is fixed on the package by the YAGlaser welding. Next, the ferrule 14 is moved in the Z directions foradjustment, and then the ferrule 14 is fixed on the fiber support by theYAG laser welding.

To irradiate each of the above welding points with the YAG laser beam, alaser output, a laser irradiation time, and a laser output distributionare experimentally examined and optimized as an irradiation condition inadvance so as to obtain a sufficient welding strength and minimize amisalignment generated in welding.

Second Example

FIG. 14 is a perspective view showing an optical transmission unitaccording to second example of the invention. This optical transmissionunit 2 is mounted within the package 11, as shown in FIG. 9. That is thesame as the case in first example, therefore, an illustration and anexplanation therefor will be omitted (that is the same in the thirdexample and subsequent examples as well).

The optical transmission unit 2 is composed of the carrier 16, thesemiconductor optical amplifying element (unillustrated) attached on thecarrier 16 through the first sub carrier 17, the first and the secondlens 20 and 22 fixed on the carrier through the first and the secondlens holder 19 and 21, the element support member 23 and the opticalisolator 24 fixed on the carrier, and the second optical device unit 3supported by the element support member 23. The second optical deviceunit 3 is composed of the small carrier 27, the semiconductor laserdevice 29 attached on the small carrier 27 through the second subcarrier 28, the third lens 26 fixed on the small carrier 27 through thethird lens holder 25.

In the optical transmission unit 2 shown in FIG. 14, an optical signalemitted from the semiconductor laser device 29 is collected in theoptical isolator 24 side though the third lens 26. The optical signalpassing through the optical isolator 24 is collected on thesemiconductor optical amplifying element 18 through the second lens 22.The optical signal is amplified and emitted by the semiconductor opticalamplifying element 18, and is injected into the optical fiber(unillustrated) through the first lens 20. The optical isolator 24prevents the light from returning to the semiconductor laser device 29.

The element support member 23 includes a small carrier holding part 23 ahaving a U-shaped cross-section vertical to the optical axis for holdingthe small carrier 27, and an upstanding part 23 b in a prismatic shapehaving a surface vertical to the optical axis. A bottom surface of theelement support member 23 closely contacts with a top surface of thecarrier 16, and it is welded to the carrier 16 at the welding points 47a and 48 a. The small carrier 27 is held in the small carrier holdingpart 23 a of the element support member 23, and a side surface verticalto the optical axis of the small carrier 27 closely contacts with asurface of the upstanding part 23 b of the element support member 23, sothe small carrier 27 is fixed on the element support member 23. Theelement support member 23 and the small carrier 27 are welded togetherat the welding points 61 a and 62 a. The upstanding part 23 b of theelement support member 23 is provided with the openings 63 a-67 a forwelding, and bottoms of the openings are welded to the small carrier 27.

The semiconductor laser device 29 is bonded to the second sub carrier 28by die bonding, and the second sub carrier 28 is fixed on the smallcarrier 27 by the AuSn solder or the like. The third lens 26 is fixed onthe third lens holder 25 at the welding points 41 a and 42 a by welding,and the third lens holder 25 is fixed on the small carrier 27 by weldingat the welding points 43 a and 44 a. The optical isolator 24 is fixed onthe carrier 16 by welding at the welding points 49 a and 50 a. Thesecond lens 22 is fixed on the second lens holder 21 by welding at thewelding points 51 a and 52 a, and the second lens holder 21 is fixed onthe carrier 16 by welding at the welding points 53 a and 54 a. Thesemiconductor optical amplifying element, which cannot be viewed becauseit is backward, is bonded to the first sub carrier 17 by die bondingusing the AuSn solder or the like, and the first sub carrier 17 issoldered to the carrier 16 using the AuSn or the like. The first lens 20is fixed on the first lens holder 19 by welding at the welding points 55a and 56 a, and the first lens holder 19 is fixed on the carrier 16 bywelding at the welding points at 57 a and 58 a. In the welding points 41a-58 a, the laser welding is performed using the YAG laser, for example.In FIG. 14, the welding points 41 b-44 b, 47 b-58 b (each of them isunillustrated) are provided in an invisible opposite side to the weldingpoints 41 a-44 a, 47 a-58 a symmetrically.

Assembly Method for Second Example

Next, an assembly method for the second example will be explained. Theassembly method for the second optical device unit 3 and a fixing methodfor the optical isolator 24, the semiconductor optical amplifyingelement, the lenses and the like on the carrier 16 are the same as thecase in first example. Hereinafter, the fixing method for the elementsupport member 23 and the second optical device unit 3 on the carrier 16on which the optical isolator 24, the semiconductor optical amplifyingelement, the lenses and the like are fixed will be explained.

While the second optical device unit 3 is gripped by a gripper and alsothe second optical device unit 3 is pressed, the side surface verticalto the optical axis of the small carrier 27 is closely contacted withthe surface of the upstanding part 23 b of the element support member23. While in the state, both are moved in the X, Y, Z directions andadjusted.

After the alignment, the element support member 23 is closely contactedwith the carrier 16 by pressing the element support member 23 on thecarrier 16 by a pressing tool, and the element support member 23 isfixed in the above state by the YAG laser welding at the welding points47 a and 47 b, 48 a and 48 b (47 b, 48 b are unillustrated). Thiswelding is performed for at least at each two-point provided to besymmetric to each other about the surface passing through the opticalaxis and vertical to the main surface of the carrier 16, i.e. at fourpoints in total, at the same time and under the same welding condition.Depending on this welding, the position of the semiconductor laserdevice 29 is fixed in the Z axis direction (an optical axis direction)and the X axis direction (a horizontal direction).

After that, the second optical device unit 3 is moved again in themovable Y direction (an upward and downward direction) to be adjusted atan optimal position. After the adjustment, the welding is performedwhile the element support member 23 is pressed on the carrier 16 by thepressing tool. That is, the element support member 23 and the smallcarrier 27 are welded together through the openings 63 a-67 a forwelding, and then the welding points 61 a and 62 a, and also the weldingpoints 61 b and 62 b (unillustrated) provided to be symmetric to 61 aand 62 a are welded together.

A different point between the first and the second example is that thefixed position of the element support member 23 of first example ischanged to be set under the small carrier 27. In the present example,the semiconductor laser device 29 can be adjusted only in one directionafter the element support member 23 is fixed on the carrier 16, so thatthe welding/fixing process for the element support member 23 in thiscase requires more strict accuracy than the case in first example inwhich the adjustment can be performed in two directions. In addition, aposition on which the emitting light from the third lens 26 is collectedis comparably away from a position on which the small carrier 27 and theelement support member 23 are welded together in the example. Therefore,the welding is required to be performed with strict accuracy in anangular alignment.

Third Example

FIG. 15 is a perspective view showing an optical transmission unit 2according to the third example of the present invention. Roughlyexplaining, the semiconductor laser device and the semiconductor opticalamplifying element are exchanged in the example, with respect to thefirst example.

As shown in FIG. 15, the optical transmission unit 2 is composed of thecarrier 16, the semiconductor laser device 29 attached on the carrier 16through the second sub carrier 28, the element support member 23 and theoptical isolator 24 which are fixed on the carrier 16, and a firstoptical device unit 4 supported by the element support member 23. Thefirst optical device unit 4 in this case is composed of the smallcarrier 27, the semiconductor optical amplifying element (unillustrated)attached on the small carrier 27 through the first sub carrier 17, thefirst and the second lenses 20 and 22 fixed through the first and thesecond lens holders 19 and 21.

In the optical transmission unit 2 shown in FIG. 15, an optical signalemitted from the semiconductor laser device 29 is collected in theoptical isolator 24 side through the third lens 26, and the opticalsignal passing through the optical isolator 24 is collected on thesemiconductor optical amplifying element through the second lens 22. Theoptical signal is amplified and emitted by the semiconductor opticalamplifying element, and is injected into the optical fiber through thefirst lens 20. The optical isolator 24 prevents the optical signal fromreturning to the semiconductor laser device 29.

The element support member 23 is in a square cylindrical shape with asquare shaped cross-section, and is provided with openings on its twosurfaces facing the optical axis direction for transmitting light. Theelement support member 23 is fixed while a bottom surface thereofclosely contacts with the carrier 16 and welded at the welding points 47b and 48 b. The second lens holder 21 includes the lens holding part 21a in a U-shape for holding the second lens 22 and a plate-like uprightpart 21 b rising upright and provided with an optical transmissive hole.

The second lens holder 21 is fixed on the element support member 23while a surface of the upright part 21 b in an element support memberside closely contacted with a side surface of the element support member23 and welded at welding points 69 b and 70 b. The semiconductor opticalamplifying element (unillustrated) is bonded to the first sub carrier 17by die bonding, and the first sub carrier 17 is soldered to the smallcarrier 27. The first lens 20 is fixed on the first lens holder 19 bywelding at the welding points 55 b and 56 b, and the first lens holder19 is fixed on the small carrier 27 by welding at the welding points 57b and 58 b. The second lens 22 is fixed on the second lens holder 21 bywelding at the welding points 51 b and 52 b, and the second lens holder21 is fixed on the small carrier 27 by welding at the welding points 53b and 54 b. Accordingly, the first optical device unit 4 is fixed on theelement support member 23 through the second lens holder 21.

The optical isolator 24 is fixed on the carrier 16 by welding atunillustrated welding points (49 b and 50 b) using the AuSn solder orthe like. The third lens 26 is fixed on the third lens holder 25 bywelding at the welding points 41 b and 42 b, and the third lens holder25 is fixed on the carrier 16 by welding at the welding points 43 b and44 b. Further, the semiconductor laser device 29 is bonded to the secondsub carrier 28 by die bonding, and the second sub carrier 28 is solderedto the carrier 16. In FIG. 15, the welding points 41 a-44 a, 47 a-58 a,69 a, 70 a (each of them is unillustrated) are provided on an invisibleopposite side from the welding points 41 b-44 b, 47 b-58 b, 69 b, 70 bsymmetrically.

An assembly method of the present example is the same as the case in thefirst example, so that a detailed explanation will be omitted. The firstoptical device unit 4 and the element support member 23 are moved in theX, Y, and Z directions to be aligned, and then the element supportmember 23 is welded and fixed on the carrier 16 while the elementsupport member 23 is pressed on the carrier 16. Next, the alignment isperformed again, and the second lens holder 21 is welded and fixed onthe element support member 23 while the first optical device unit 4 ispressed on the element support member 23.

Fourth Example 4

FIG. 16 is a perspective view showing an optical transmission unitaccording to the fourth example of the present invention. The fourthexample is different from the third example in that the position of theelement support member in the third example is changed to be set underthe small carrier 27. The element support member used in the presentexample is the same as in the second example, therefore, a relationshipbetween the present example and the third example is the same as the onebetween first and second example.

As shown in FIG. 16, the optical transmission unit 2 is composed of thecarrier 16 to be a base, the semiconductor laser device 29 attached onthe carrier 16 through the second sub carrier 28, the element supportmember 23 and the optical isolator 24 which are fixed on the carrier 16,and the first optical device unit 4 supported by the element supportmember 23. The first optical device unit 4 is composed of the smallcarrier 27, the semiconductor optical amplifying element (unillustrated)attached on the small carrier 27 through the first sub carrier 17, andthe first and the second lenses 20 and 22 fixed through the first andsecond lens holders 19 and 21.

The element support member 23 includes the small carrier holding part 23a having the U-shaped cross-section vertical to the optical axis forholding the small carrier 27, and the upstanding part 23 b in aprismatic shape having a surface vertical to the optical axis. A bottomsurface of the element support member 23 closely contacts with an uppersurface of the carrier 16, and welded to the carrier 16 at the weldingpoints 47 b and 48 b. The small carrier 27 is held in the small carrierholding part 23 a of the element support member 23, and the side surfacevertical to the optical axis of the small carrier 27 closely contactswith the surface of the upstanding part 23 b of the element supportmember 23, and the small carrier is fixed on the element support member23. The element support member 23 and the small carrier 27 are weldedtogether at the welding points 61 b and 62 b. Further, the upstandingpart 23 b of the element support member 23 is provided with openings 63a-67 a for welding, and the welding with the small carrier 27 isperformed at bottoms of the openings.

The semiconductor optical amplifying element which is behind and cannotbe viewed is bonded to the first sub carrier 17 by die bonding, and thefirst sub carrier 17 is soldered to the small carrier 27 using the AuSnsolder or the like. The first lens 20 is fixed on the first lens holder19 by welding at the welding points 55 b and 56 b, and the first lensholder 19 is fixed on the small carrier 27 by welding at the weldingpoints 57 b and 58 b. Further, the second lens 22 is fixed on the secondlens holder 21 by welding at the welding points 51 b and 52 b, and thesecond lens holder 21 is fixed on the small carrier 27 by welding at thewelding points 53 b and 54 b.

The optical isolator 24 is fixed on the carrier 16 by welding at thewelding points 49 b and 50 b. The third lens 26 is fixed on the thirdlens holder 25 by welding at the welding points 41 b and 42 b. The thirdlens holder 25 is fixed on the carrier 16 by welding at the weldingpoints 43 b and 44 b. The semiconductor laser device 29 is bonded to thesecond sub carrier 28 by die bonding, and the second sub carrier 28 issoldered to the carrier 16 with the AuSn solder or the like. Note thatin FIG. 16, the welding points 41 a-44 a, 47 a-58 a (each of them isunillustrated) are provided in an invisible opposite side from thewelding points 41 b-44 b, 47 b-58 b symmetrically.

Fifth Example

FIG. 17 is a perspective view showing an optical transmission unitaccording to the fifth example of the present invention. In the opticaltransmission module of the present example, a passive planar lightwavecircuit is mounted instead of the semiconductor laser device.

The optical transmission unit 2 of the present example is composed ofthe carrier 16, the semiconductor optical amplifying element(unillustrated) attached on the carrier 16 through the first sub carrier17, the first and the second lenses 20 and 22 fixed on the carrierthrough the first and the second lens holders 19 and 21, the elementsupport member 23 fixed on the carrier, and the second optical deviceunit 3 supported by the element support member 23. The second opticaldevice unit 3 is composed of the small carrier 27, and the planarlightwave circuit 30 attached on the small carrier 27.

In the optical transmission unit 2 shown in FIG. 17, an optical signalemitted from the semiconductor optical amplifying element at its end inthe second lens 22 side is collected on the planar lightwave circuit 30through the second lens 22 and light transmissive holes of the elementsupport member 23 and a small carrier 27. The optical signal isprocessed in this circuit, and is returned to the semiconductor opticalamplifying element. The optical signal is amplified and emitted by thesemiconductor optical amplifying element, and is injected into theoptical fiber (unillustrated) through the first lens 20.

The element support member 23 of the present example is a plate-likestructural object having an opening for transmitting light, and itsbottom surface closely contacts with an upper surface of the carrier 16,and is welded to the carrier 16 at the welding points 47 a and 48 a.Further, the small carrier 27 of the present example includes an elementmounting part 27 a parallel to the carrier 16 and an upright part 27 brising vertically from the element mounting part 27 a and having anoptical transmissive hole. The small carrier 27 closely contacts with amain surface of the element support member 23 at its surface of theupright part 27 b in a semiconductor optical amplifier side, and isfixed on the element support member 23 by welding at the welding points59 a and 60 a.

The second lens 22 is fixed on the second lens holder 21 by welding atthe welding points 51 a (unillustrated), 52 a, and the second lensholder 21 is fixed on the carrier 16 by welding at the welding point 53a (unillustrated) and 54 a. The semiconductor optical amplifying element(unillustrated) is bonded to the first sub carrier 17 by die bonding,and the first sub carrier 17 is soldered to the carrier 16. The firstlens 20 is fixed on the first lens holder 19 by welding at the weldingpoints 55 a and 56 a, and the first lens holder 19 is fixed on thecarrier 16 by welding at welding points 57 a and 58 a. In FIG. 17, thewelding points 47 b, 48 b, 51 b-60 b (each of them is unillustrated) areprovided in an invisible opposite side from the welding points 47 a, 48a, 51 a-60 a symmetrically.

Assembly Method for Fifth Example

Next, an assembly method for the fifth example will be explained. Theplanar lightwave circuit 30 is mounted on the element mounting part 27 aof the small carrier 27 so as to compose the second optical device unit3, and the semiconductor optical amplifying element, the first and thesecond lenses, and the first and the second lens holders are mounted onthe carrier 16 as in the same manner with the first example.

While causing the semiconductor optical amplifying element to emitlight, the second optical device unit 3 is gripped by a gripper in astate in which facing surfaces of the small carrier 27 and the elementsupport member 23 closely contact with each other. The second opticaldevice unit 3 is then moved in the X, Y, and Z directions and adjustedso that an optical output becomes the maximum. After the adjustment, theelement support member 23 is pressed on the carrier 16 by the pressingtool so that the element support member 23 and the carrier 16 closelycontacts with each other. Then, the element support member 23 is fixedin the above mentioned state by welding at the welding points 47 a and47 b, 48 a and 48 b (47 b and 48 b are unillustrated) with the YAG laserwelding.

After that, the second optical device unit 3 is moved again in themovable X and Y directions to be adjusted at an optimal position. Afterthe adjustment, the element support member 23 and the small carrier 27is welded at the welding points 59 a and 60 a while the small carrier 27is pressed on the element support member 23 by a pressing tool.

In the present example, the element support member 23 is arrangedbetween the second lens 22 and the planar lightwave circuit 30, so thata displacement of an injecting position for the emitted light, which iscaused by an angular misalignment in welding, can be reduced.

Sixth Example

FIG. 18 is a perspective view of an optical transmission unit 2according to the sixth example of the present invention. The sixthexample is different from the fifth example in that the position of theelement support member in the fifth example is changed and is placedunder the small carrier 27. The element support member used in thepresent example is the same as the one in the sixth example. Therefore,the sixth example and the fifth example are in the same relationship ofthe second and the first examples 2 and 1.

As shown in FIG. 18, the optical transmission unit 2 in the exemplaryembodiment is composed of the carrier 16, the semiconductor opticalamplifying element (unillustrated) attached on the carrier 16 throughthe first sub carrier 17, the first and the second lenses 20 and 22fixed on the carrier through the first and the second lens holders 19and 21, the element support member 23 fixed on the carrier 16, and thesecond optical device unit 3 supported by the element support member 23.The second optical device unit 3 is composed of the small carrier 27,and the planar lightwave circuit 30 attached on the small carrier 27.

A bottom surface of the element support member 23 closely contacts withan upper surface of the carrier 16, and is welded to the carrier 16 atthe welding points 47 a and 48 a. The small carrier 27 held by the smallcarrier holding part 23 a of the element support member 23 is fixed onthe element support member 23 while a small carrier's side surfacevertical to the optical axis closely contacts with the surface of theupstanding part 23 b of the element support member 23. The elementsupport member 23 and the small carrier 27 are welded at the weldingpoints 61 a and 62 a. Further, the upstanding part 23 b of the elementsupport member 23 is provided with the opening 63 a-67 a for welding,and the welding to the small carrier 27 is performed at bottoms of theopenings.

The second lens 22 is fixed on the second lens holder 21 by welding atthe welding points 51 a and 52 a, and the second lens holder 21 is fixedon the carrier 16 by welding at the welding points 53 a and 54 a. Thesemiconductor optical amplifying element is bonded to the first subcarrier 17 by die bonding, and the first sub carrier 17 is soldered tothe carrier 16. The first lens 20 is fixed on the first lens holder bywelding at the welding points 55 a and 56 a, and the first lens holder19 is fixed on the carrier 16 by welding at the welding points 57 a and58 a. In FIG. 18, the welding points 47 b, 48 b, 51 b-58 (each of themis unillustrated) are provided in an invisible opposite side from thewelding points 47 a, 48 a, 51 a-58 a symmetrically.

Seventh Example

FIG. 19 is a perspective view showing an optical transmission unit 2according to the seventh example of the present invention. Roughlyexplaining, in the present example, the planar lightwave circuit changesits position with the semiconductor optical amplifying element in thefifth example. As shown in FIG. 19, the optical transmission unit 2 iscomposed of the carrier 16, the planar lightwave circuit 30 attached onthe carrier 16, the element support member 23 fixed on the carrier 16,and the first optical device unit 4 supported by the element supportmember 23. The first optical device unit 4 is composed of the smallcarrier 27, the semiconductor optical amplifying element (unillustrated)attached on the small carrier 27 through the first sub carrier 17, thefirst and the second lenses 20 and 22 fixed through the first and secondlens holders 19 and 21.

The element support member 23 of the present example is a plate-likestructural object having an opening for transmitting light, and a bottomthereof closely contacts with an upper surface of the carrier 16, and iswelded with the carrier 16 at the welding points 47 b and 48 b. Further,the second lens holder 21 includes the lens holding part 21 a in aU-shape for holding the second lens 22 and the platy upright part 21 brising vertically and provided with an optical transmissive hole. Whilea surface of upright part 21 b in an element support member 23 sideclosely contacts with a main surface of the element support member 23,the upright part is fixed on the element support member 23 by welding atthe welding points 69 b and 70 b. The semiconductor optical amplifyingelement (unillustrated) is bonded to the first sub carrier 17 by diebonding, and the first sub carrier 17 is soldered to the small carrier27 with the AuSn solder or the like.

The first lens 20 is fixed on the first lens holder 19 by welding at thewelding points 55 b and 56 b, the first lens holder 19 is fixed on thesmall carrier 27 by welding at the welding points 57 b and 58 b. Thesecond lens 22 is fixed on the second lens holder 21 by welding at thewelding points 51 b and 52 b, the second lens holder 21 is fixed on thesmall carrier 27 by welding at the welding points at 53 b and 54 b.Accordingly, the first optical device unit 4 is fixed with the elementsupport member 23 through the second lens holder 21.

An assembly method for the present example is the same as in the thirdexample. In FIG. 19, the welding points 47 a, 48 a, 51 a-58 a, 69 a, 70a (each of them is unillustrated) are provided in an invisible oppositeside from the welding points 47 b, 48 b, 51 b-58 b, 69 b, 70 bsymmetrically.

FIG. 20 is a perspective view showing an optical transmission unit 2according to the eighth example of the invention. The eighth example isdifferent from the seventh example in that the position of the elementsupport member of seventh example is changed and is placed under thesmall carrier 27. The element support member used in the present exampleis the same as the one in the sixth example. Therefore, a relationshipbetween the present example and the seventh example is the same as inthe fifth and the sixth examples.

As shown in FIG. 20, the optical transmission unit 2 of the presentexample is composed of the carrier 16, the planar lightwave circuit 30attached on the carrier 16, the element support member 23 fixed on thecarrier 16, and the first optical device unit 4 supported by the elementsupport member 23. The first optical device unit 4 is composed of thesmall carrier 27, the semiconductor optical amplifying element(unillustrated) attached on the small carrier 27 through the first subcarrier 17, and the first and the second lenses 20 and 22 fixed throughthe first and the second lens holders 19 and 21.

A bottom surface of the element support member 23 closely contacts withan upper surface of the carrier 16, and the element support member iswelded to the carrier 16 at the welding points 47 b and 48 b. The smallcarrier 27 is held in the small carrier holding part 23 a of the elementsupport member 23, and a side surface of the small carrier 27, which isvertical to the optical axis, closely contacts with the surface of theupstanding part 23 b of the element support member 23, and is fixed onthe element support member 23. The element support member 23 and thesmall carrier 27 are welded together at the welding points 61 b and 62b. The upstanding part 23 b of the element support member 23 is providedwith the openings 63 a-67 a for welding, and the welding to the smallcarrier 27 is performed at bottoms of those openings.

The semiconductor optical amplifying element (unillustrated) is bondedto the first sub carrier 17 by die bonding, the first sub carrier 17 issoldered on the small carrier 27 with the AuSn solder or the like. Thefirst lens 20 is fixed on the first lens holder 19 by welding at thewelding points 55 b and 56 b, and the first lens holder 19 is fixed onthe small carrier 27 by welding at the welding points 57 b and 58 b. Thesecond lens 22 is fixed on the second lens holder 21 by welding atwelding points 51 b and 52 b, and the second lens holder 21 is fixed onthe small carrier 27 by welding at welding points 53 b and 54 b.

An assembly method for the present example is the same as the case inthe fourth example. In FIG. 20, the welding points 47 a, 48 a, 51 a-58(each of them are unillustrated) are provided in an invisible oppositeside from the welding points 47 b, 48 b, 51 b-58 b symmetrically.

INDUSTRIAL APPLICABILITY

According to the present invention, either the first or the secondoptical devices is fixed on the carrier, and the other one is fixed onthe element support member while its second surface (vertical to theoptical axis) closely contacts with the element support member. Thus,the other optical device can be fixed in the X-Y plane after alignmentwith the optical axis of the one optical device.

While the invention has been particularly shown and described withreference to exemplary embodiments thereof, the invention is not limitedto these embodiments. It will be understood by those of ordinary skillin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present invention asdefined by the claims.

This application is based upon and claims the benefit of priority fromJapanese patent application No. 2005-264723, filed on Sep. 13, 2005, thedisclosure of which is incorporated herein in its entirety by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] A cross-sectional view showing an optical transmission moduleaccording to a first exemplary embodiment of the invention;

[FIG. 2] A perspective view showing an optical transmission unitaccording to the first exemplary embodiment of the present invention;

[FIG. 3] A perspective view showing an optical transmission unitaccording to a second exemplary embodiment of the present invention;

[FIG. 4] A cross-sectional view explaining a difference between thefirst and the second exemplary embodiments;

[FIG. 5] A perspective view showing an optical transmission unitaccording to a third exemplary embodiment of the invention;

FIG. 6( a) is a cross-sectional view taken along line A-A in FIG. 5,FIG. 6( b) is a cross-sectional view taken along line B-B in FIG. 5;

[FIG. 7] A perspective view showing a modified first exemplaryembodiment;

[FIG. 8] A perspective view showing a modified third exemplaryembodiment;

[FIG. 9] A cross-sectional view showing an optical transmission moduleaccording to a first example;

[FIG. 10] A perspective view showing an optical transmission unitaccording to the first example;

FIG. 11( a) is a perspective view explaining a welding point between theelement support member and the third lens holder in the first example,FIGS. 11( b) and 11(c) are cross-sectional views for the same;

[FIG. 12] Cross-sectional views showing an assembly method for the firstexample in its process sequence;

[FIG. 13] Front views explaining welding processes between the elementsupport member and the third lens holder in the first example;

[FIG. 14] A perspective view showing an optical transmission unitaccording to the second example;

[FIG. 15] A perspective view showing an optical transmission unitaccording to the third example;

[FIG. 16] A perspective view showing an optical transmission unitaccording to the fourth example;

[FIG. 17] A perspective view showing an optical transmission unitaccording to the fifth example;

[FIG. 18] A perspective view showing an optical transmission unitaccording to the sixth example;

[FIG. 19] A perspective view showing an optical transmission unitaccording to the seventh example;

[FIG. 20] A perspective view showing an optical transmission unitaccording to the eighth example;

[FIG. 21] A cross-sectional view showing a related example; and

[FIG. 22] A perspective view showing a lens and a lens holder used inthe related example.

DESCRIPTION OF THE CODES

-   -   1 OPTICAL TRANSMISSION MODULE    -   2 OPTICAL TRANSMISSION UNIT    -   3 SECOND OPTICAL DEVICE UNIT    -   4 FIRST OPTICAL DEVICE UNIT    -   11, 111 PACKAGE    -   12, 112 PELTIER DEVICE    -   13, 113 FIBER SUPPORT    -   14, 114 FERRULE    -   15, 115 OPTICAL FIBER    -   16, 116 CARRIER    -   17, 117 FIRST SUB CARRIER    -   18 SEMICONDUCTOR OPTICAL AMPLIFYING ELEMENT    -   118 FIRST OPTICAL DEVICE    -   19, 119 FIRST LENS HOLDER    -   20, 120 FIRST LENS    -   21, 121 SECOND LENS HOLDER    -   21 a LENS HOLDING PART    -   21 b UPRIGHT PART    -   22, 122 SECOND LENS    -   23, 123 ELEMENT SUPPORT MEMBER    -   23 a, 123 a SMALL CARRIER HOLDING PART    -   23 b, 123 b UPSTANDING PART    -   123 c UPRIGHT PART    -   24, 124 OPTICAL ISOLATOR    -   25, 125 THIRD LENS HOLDER    -   25 a, 125 a LENS HOLDING PART    -   25 b, 125 b UPRIGHT PART    -   25 c TAPER PART    -   25 d THIN PART    -   26, 126 THIRD LENS    -   27, 127 SMALL CARRIER    -   27 a, 127 a ELEMENT MOUNTING PART    -   27 b, 127 b UPRIGHT PART    -   28, 128 SECOND SUB CARRIER    -   29 SEMICONDUCTOR LASER DEVICE    -   129 SECOND OPTICAL DEVICE    -   30 PLANAR LIGHTWAVE CIRCUIT    -   31 CLIP    -   32 GRIPPER    -   33 OPTICAL POWER METER    -   34 PRESSING TOOL    -   35 PUSHER    -   35 a PUSHED AREA    -   41 a-62 a, 68 a, 69 a WELDING POINT    -   63 a-67 a OPENING FOR WELDING

1-38. (canceled)
 39. An optical transmission module comprising: a firstoptical device arranged in an output side; a second optical devicearranged in alignment with the first optical device with respect tothose optical axes; a carrier on which either the first or the secondoptical device is fixed; an element support member having a firstsurface parallel to the optical axis and a second surface vertical tothe optical axis; a package for housing the first and the second opticaldevices, the carrier, and the element support member; and an opticalguide unit for guiding light emitted from the first optical device tooutside the package; wherein the element support member is fixed on thecarrier at the first surface thereof, and the other one of the first andthe second optical devices is fixed on the second surface of the elementsupport member.
 40. The optical transmission module, as claimed in claim39, wherein the first optical device is a semiconductor opticalamplifying element for amplifying an incident optical signal.
 41. Theoptical transmission module, as claimed in claim 39, wherein the firstoptical device is fixed on the carrier through a sub carrier.
 42. Theoptical transmission module, as claimed in claim 39, wherein a firstlens is arranged at the optical guide unit side of the first opticaldevice, and a second lens is arranged at a second optical device side ofthe first optical device respectively; and the first lens and the secondlens are fixed on the carrier through a first lens holder and a secondlens holder respectively.
 43. The optical transmission module, asclaimed in claim 39, wherein the second optical device is asemiconductor laser device, and the semiconductor laser device is fixedon the element support member through a sub carrier, a small carrier,and a third lens holder holding a third lens.
 44. The opticaltransmission module, as claimed in claim 43, wherein the third lensholder includes a lens holding part in a U-shape for holding the thirdlens, and an plate-like upright part fixed at a light emitting side ofthe lens holding part, and the third lens holder is fixed on the smallcarrier at the lens holding part thereof, and is fixed on the elementsupport member at the upright part thereof.
 45. The optical transmissionmodule, as claimed in claim 39, wherein the second optical device is asemiconductor laser device, and the semiconductor laser device is fixedwith the element support member through a sub carrier and a smallcarrier.
 46. The optical transmission module, as claimed in claim 45,wherein the small carrier has an L-shaped cross-section vertical to thecarrier and parallel to the optical axis, the horizontal part thereof isfixed to the second optical device, and the vertical part thereof isfixed to the element support member.
 47. The optical transmissionmodule, as claimed in claim 45, wherein the third lens holder holdingthe third lens is fixed in a light emitting side of the second opticaldevice on the small carrier.
 48. The optical transmission module, asclaimed in claim 39, wherein the element support member is in a squarecylindrical shape having a square shaped cross-section, a bottom surfaceof the square barrel-shaped body is the first surface, and a sidesurface of the square barrel-shaped body is the second surface.
 49. Theoptical transmission module, as claimed in claim 39, wherein the elementsupport member is in a square barrel shape with one side surface openedhaving a U-shaped cross-section, a bottom surface of the squarebarrel-shaped body with one side surface opened is the first surface,and an opening side surface of the square barrel-shaped body with oneside surface opened is the second surface.
 50. The optical transmissionmodule, as claimed in claim 48, wherein the element support memberhouses an optical isolator fixed on the carrier.
 51. The opticaltransmission module, as claimed in claim 39, wherein the second opticaldevice is a planar lightwave circuit into/from which an optical signalis injected and emitted, and the planar lightwave circuit is fixed onthe element support member through a small carrier.
 52. The opticaltransmission module, as claimed in claim 51, wherein the small carrierhas an L-shaped cross-section vertical to the carrier and parallel tothe optical axis, the horizontal part thereof is fixed to the secondoptical device, and the vertical part thereof is fixed to the elementsupport member.
 53. The optical transmission module, as claimed in claim39, wherein the element support member has a plate-like body having amain surface orthogonal to the optical axis, a bottom surface of theplate-like body is the first surface, and a main surface at a secondoptical device side of the plate-like body is the second surface. 54.The optical transmission module, as claimed in claim 39, wherein theelement support member includes a small carrier holding part in aU-shape for holding the small carrier and a columnar upstanding partfixed on a side surface vertical to the optical axis of the smallcarrier, and a bottom surface thereof is the first surface and a surfaceat a small carrier side of the upstanding part is the second surface.55. The optical transmission module, as claimed in claim 54, wherein theupstanding part of the element support member is provided with aplurality of openings for welding parallel to the optical axis, and theplurality of openings is arranged parallel to a main surface of thecarrier.
 56. The optical transmission module, as claimed in claim 39,wherein the first optical device is fixed on the element support memberthrough a sub carrier and a small carrier.
 57. The optical transmissionmodule, as claimed in claim 39, wherein the first lens is arranged at anoptical guide unit side of the first optical device, the second lens isarranged at a second optical device side of the first optical device,and the first lens and the second lens are fixed on the small carrierthrough the first lens holder and the second lens holder respectively.58. The optical transmission module, as claimed in claim 57, wherein thesecond lens holder includes a U-shaped lens holding part for holding thesecond lens, and an platy upright part fixed on an light injecting sideof the lens holding part, and the second lens holder is fixed on thesmall carrier at the lens holding part thereof and is fixed on theelement support member at the upright part thereof.
 59. The opticaltransmission module, as claimed in claim 57, wherein the small carrierhas a roughly L-shaped cross-section vertical to the carrier andparallel to the optical axis, the horizontal part thereof is fixed tothe second optical device, and the vertical part thereof is fixed to theelement support member.
 60. The optical transmission module, as claimedin claim 56, wherein the element support member is in a square barrelshape having a square shaped cross-section, and a bottom surface of thesquare barrel-shaped body is the first surface and one side surface ofthe square barrel-shaped body is the second surface.
 61. The opticaltransmission module, as claimed in claim 56, wherein the element supportmember is in a square barrel shape with one side opened having aU-shaped cross-section, and a bottom of the square barrel-shaped bodywith one side opened is the first surface and an opening side surface ofthe square barrel-shaped body with one side opened is the secondsurface.
 62. The optical transmission module, as claimed in claim 60,wherein the element support member houses an optical isolator fixed onthe carrier.
 63. The optical transmission module, as claimed in claim56, wherein the element support member is in a platy shape having a mainsurface orthogonal to the optical axis, a bottom surface of theplate-like body is the first surface and a main surface at a secondoptical device side of the plate-like body is the second surface. 64.The optical transmission module, as claimed in claim 56, wherein theelement support member includes a small carrier holding part in aU-shape for holding the small carrier and a columnar upstanding partfixed on a side surface at an optical guide unit side of the smallcarrier holding part, and a bottom surface thereof is the first surfaceand a surface at the small carrier side of the upstanding part is thesecond surface.
 65. The optical transmission module, as claimed in claim64, wherein the upstanding part of the element support member isprovided with a plurality of openings parallel to the optical axis forwelding, and the plurality of openings is arranged parallel to a mainsurface of the carrier.
 66. The optical transmission module, as claimedin claim 56, wherein the second optical device is a semiconductor laserdevice, and the semiconductor laser device is fixed on the carrierthrough a sub carrier.
 67. The optical transmission module, as claimedin claim 66, wherein a third lens holder for holding a third lens isfixed in a light emitting side of the second optical device on thecarrier.
 68. The optical transmission module, as claimed in claim 63,wherein the second optical device is a planar lightwave circuitinto/from which an optical signal is injected and emitted, and theplanar lightwave circuit is fixed on the carrier.
 69. The opticaltransmission module, as claimed in claim 41, wherein at least the fixingof the element support member on the carrier, and the fixing of thesmall carrier or the lens holder on the element support member areperformed by welding.
 70. The optical transmission module, as claimed inclaim 69, wherein the small carrier or the lens holder is welded to theelement support member at a thin part formed within or inside the smallcarrier or the lens holder.
 71. The optical transmission module, asclaimed in claim 70, wherein the small carrier or the lens holder has anopening or a concave part therein or inside thereof for forming the thinpart.
 72. An optical transmission module comprising: a first opticaldevice arranged in an output side; a second optical device arranged inalignment with the first optical device with respect to those opticalaxes; a carrier on which either the first or the second optical deviceis fixed; an element support member having a first surface parallel tothe optical axis and a second surface vertical to the optical axis; apackage for housing the first and the second optical devices, thecarrier, and the element support member; and an optical guide means forguiding light emitted from the first optical device to outside thepackage; wherein the element support member is fixed on the carrier atthe first surface thereof, and the other one of the first and the secondoptical devices is fixed on the second surface of the element supportmember.
 73. A manufacturing method for an optical transmission modulewhich includes a first optical device arranged in an output side, asecond optical device arranged in alignment with the first opticaldevice with respect to their optical axes, a carrier on which either thefirst or the second optical device is fixed, an element support memberincluding a first surface parallel to the optical axis and a secondsurface vertical to the optical axis, a package for housing the firstand the second optical devices, the carrier, and the element supportmember, and a light guide unit for guiding light emitted from the firstoptical device to outside of the package, wherein the element supportmember is fixed on the carrier at the first surface thereof, and theother one of the first and the second optical devices is fixed at thesecond surface thereof, the method comprising: (1) fixing either thefirst or the second optical device on the carrier; (2) adjusting aposition of the element support member while the other one of the firstand the second optical devices closely contacts with the second surfaceof the element support member, and fixing the element support member onthe carrier; and (3) aligning the first optical device and the secondoptical device with respect to those optical axes while the other one ofthe first and the second optical devices closely contacts with thesecond surface of the element support member, and fixing the other oneof the first and the second optical devices on the second surface of theelement support member.
 74. The manufacturing method for the opticaltransmission module, as claimed in claim 73, wherein, in the step (2),the element support member is fixed on the carrier by welding at leastat each two-point at the same time provided to be symmetric to eachother about a surface passing through the optical axis and vertical to amain surface of the carrier 16, and the welding is performed at least atfour points in total.
 75. The manufacturing method for the opticaltransmission module, as claimed in claim 73, wherein the element supportmember is pressed on the carrier during a fixing work in the step (2).76. The manufacturing method for the optical transmission module, asclaimed in claim 73, wherein, in the step (3), welding is performedwhile the other one of the first and the second optical devices isapplied a pressure in the optical direction at a plurality of pointsthereof centering the optical axis.
 77. The manufacturing method for theoptical module, as claimed in claim 73, wherein, in the step (3),welding is simultaneously performed at two points point-symmetric withrespect to the optical axis, or two points plain-symmetric with respectto a surface passing through the optical axis and vertical to a mainsurface of the carrier.